many, many people grow at home and never get caught. but there are a few ways that i know of. spike in electricity bill can raise some red flags, they can also fly over your house and use this thing that shows high sources of heat (lighting). other things to worry about are smell, and leaving empty bottles of nutes for everyone to see in the garbage. but as long as you tell no one, than you should be fine.

Police have been known to watch hydroponic stores, so even though you paid cash it doesn't mean that someone didn't take down your plate # for a closer look at you somewhere down the line. Possible odor detection, and putting stuff in your trash like used fertilizer bottles/other grow-related garbage are a couple of other ways to get caught.

dont tell anybody on the planet that your doing wat ur doing. and make sure you dispose of your chemicals properly and be careful where you get your supplies because some of those stores are hot and police will sit outside and document who goes inside. which isnt illegal really but it does give them an excuse to "investigate"